Tag Archives: Physics

Lockheed Martin To Develop New Missle Defense Laser System

The Missile Defense Agency, a part of the Department of Defense, awarded Lockheed Martin a nine month, $25.5 million contract extension to continue development of its Low Power Laser Demonstrator (LPLD) missile interceptor concept. This program, awarded Aug. 31, builds on a 2017 contract to develop an initial LPLD concept.

Lockheed Martin’s LPLD concept consists of a fiber laser system on a high-performing, high-altitude airborne platform. LPLD is designed to engage missiles during their boost phase – the short window after launch – which is the ideal time to destroy the threat, before it can deploy multiple warheads and decoys.

Over the course of this contract, Lockheed Martin will mature its LPLD concept to a tailored critical design review phase, which will bring the design to a level that can support full-scale fabrication.

“We have made great progress on our LPLD design, and in this stage we are particularly focused on maturing our technology for beam control – the ability to keep the laser beam stable and focused at operationally relevant ranges,” said Sarah Reeves, vice president for Missile Defense Programs at Lockheed Martin Space.

“LPLD is one of many breakthrough capabilities the Missile Defense Agency is pursuing to stay ahead of rapidly-evolving threats, and we’re committed to bringing together Lockheed Martin’s full expertise in directed energy for this important program.”

Lockheed Martin expands on advanced technology through its laser device, beam control capabilities, and platform integration – ranging from internal research and development investments in systems like ATHENA to programs such as LANCE for the Air Force Research Laboratory.

Continued LPLD development will take place at Lockheed Martin’s Sunnyvale, California campus through July 2019.

As a proven world leader in systems integration and development of air and missile defense systems and technologies, Lockheed Martin has already delivered the U.S.  several high-quality missile defense solutions that protect citizens, critical assets and deployed forces from current and future threats.

The company’s experience spans directed energy systems development, missile design and production, hit-to-kill capabilities, infrared seekers, command and control/battle management, and communications, precision pointing and tracking optics, radar and signal processing, as well as threat-representative targets for missile defense tests.

Catching Them In The Act: Hyper Fast Camera Captures Atoms In Motion

An extremely fast “electron camera” at the Department of Energy’s SLAC National Accelerator Laboratory has produced the most detailed atomic movie of the decisive point where molecules hit by light can either stay intact or break apart.

The results could lead to a better understanding of how molecules respond to light in processes that are crucial for life, like photosynthesis and vision, or that are potentially harmful, such as DNA damage from ultraviolet light.

In the study, published in Science, researchers looked at a gas whose molecules have five atoms each. They watched in real time how light stretched the bond between two atoms in the molecules to a “point of no return,” sending the molecules on a path that either further separated the atoms and cleaved the bond or caused the atoms to vibrate while preserving the bond.

“The starting and end points of a chemical reaction are often obvious, but it’s much more challenging to take snapshots of the rapid reaction steps in between,” said postdoctoral researcher Jie Yang, the study’s lead author from SLAC’s Accelerator Directorate and the Stanford PULSE Institute.

“The crossroads where a molecule can do one thing or another are an important factor in determining the outcome of a reaction. Now we’ve been able to observe directly for the first time how the atomic nuclei of a molecule rearrange at such an intersection.”

Co-author Todd Martinez, a professor at SLAC and Stanford University and an investigator at PULSE, said, “The system we studied is a paradigm for the much more complex light-driven reactions in nature.” For example, the absorption of ultraviolet light can cause damage to DNA, but other mechanisms turn the light’s energy into molecular vibrations and minimize the harmful effect.

Ultra-High-Speed Snapshots of Atoms in Motion
The first steps in light-driven reactions are extremely fast. Molecules absorb light almost instantaneously, leading to a rapid rearrangement of their electrons and atomic nuclei. To see what happens in real time, researchers need ultra-high-speed cameras that can “freeze” motions occurring within femtoseconds, or millionths of a billionth of a second.

The camera used in the study was an instrument for ultrafast electron diffraction (UED), in which a high-energy beam of electrons probes the interior of a sample, generating snapshots of its atomic architecture at different points in time during a chemical reaction. Strung together, these snapshots turn into a movie of the speedy atomic motions.

At SLAC, the researchers flashed laser light into a gas of trifluoroiodomethane molecules and observed over the course of hundreds of femtoseconds how bonds between carbon and iodine atoms elongated to a point at which the bond either broke, splitting off iodine from the molecules, or contracted, setting off vibrations of the atoms along the bond.

“UED was absolutely crucial to seeing that point during the reaction,” said physicist Xijie Wang, head of SLAC’s UED program and the study’s principal investigator. “Other methods either don’t detect nuclear motions directly or haven’t reached the resolution necessary to make this kind of observation in gases.”

Mapping Energy Landscapes of Chemical Reactions
The observation is in agreement with calculations that provide a deeper understanding of what happens during the reaction.

The laser light “energizes” the molecules, elevating them from a low-energy ground state to a higher-energy excited state (see image below). Molecular states like these can be described by energy landscapes, with mountains of more energy and valleys of less energy. Like a golf ball rolling on a curved putting green, the molecules can follow reaction paths on these surfaces.

When the landscapes of different molecular states intersect, the reaction can proceed in several directions. Chemists call this point a conical intersection.

In fact, molecules at conical intersections exist in several states at once – an oddity rooted in the fact that molecules are tiny quantum systems, said co-author Xiaolei Zhu, a postdoctoral researcher at PULSE and Stanford. “We can predict this behavior in computer simulations,” he said. “Now we’ve also directly seen that the molecules behave exactly that way in the experiment.”

The team is now planning the next steps. “We’re continuing to develop the UED method so that we can look at similar processes in liquids,” Wang said. “This will bring us even closer to understanding light-driven chemical reactions in biological environments.”

UC Berkley Develops New Technology To Make Superior Lithium Batteries Cheap As Dirt

Lithium-based batteries use more than 50 percent of all cobalt produced in the world. These batteries are in your cell phone, laptop and maybe even your car. About 50 percent of the world’s cobalt comes from the Congo, where it’s largely mined by hand, in some instances by children.  Cobalt is expensive.

But now, a research team led by scientists at the University of California, Berkeley, has opened the door to using other metals in lithium-based batteries, and have built cathodes with 50 percent more lithium-storage capacity than conventional materials.

“We’ve opened up a new chemical space for battery technology,” said senior author Gerbrand Ceder, professor in the Department of Materials Science and Engineering at Berkeley. “For the first time we have a really cheap element that can do a lot of electron exchange in batteries.”

The study will be published in the April 12 edition of the journal Nature. The work was a collaboration between scientists at UC Berkeley, Berkeley Lab, Argonne National Lab, MIT and UC Santa Cruz.

In today’s lithium-based batteries, lithium ions are stored in cathodes (the negatively charged electrode), which are layered structures. Cobalt is crucial to maintaining this layered structure. When a battery is charged, lithium ions are pulled from the cathode into the other side of the battery cell, the anode.

The absence of lithium in the cathode leaves a lot of space. Most metal ions would flock into that space, which would cause the cathode to lose its structure. But cobalt is one of the few elements that won’t move around, making it critical to the battery industry.

In 2014, Ceder’s lab discovered a way that cathodes can maintain a high energy density without these layers, a concept called disordered rock salts. The new study shows how manganese can work within this concept, which is a promising step away from cobalt dependence because manganese is found in dirt, making it a cheap element.

“To deal with the resource issue of cobalt, you have to go away from this layeredness in cathodes,” Ceder said. “Disordering cathodes has allowed us to play with a lot more of the periodic table.”

In the new study, Ceder’s lab shows how new technologies can be used to get a lot of capacity from a cathode. Using a process called fluorine doping, the scientists incorporated a large amount of manganese in the cathode. Having more manganese ions with the proper charge allows the cathodes to hold more lithium ions, thus increasing the battery’s capacity.

Other research groups have attempted to fluorine dope cathodes but have not been successful. Ceder says his lab’s work on disordered structures was a big key to their success.

Cathode performance is measured in energy per unit weight, called watt-hours per kilogram. The disordered manganese cathodes approached 1,000 watt-hours per kilogram. Typical lithium-ion cathodes are in the range of 500-700 watt-hours per kilogram.

“In the world of batteries, this is a huge improvement over conventional cathodes,” said lead author Jinhyuk Lee, who was a postdoctoral fellow at Ceder’s lab during the study, and is now a postdoctoral fellow at MIT.

The technology needs to be scaled up and tested more to see if it can be used in applications like laptops or electric vehicles. But Ceder says whether or not this technology actually makes it inside a battery is beside the point; the researchers have opened new possibilities for the design of cathodes, which is even more important.

“You can pretty much use any element in the periodic table now because we’ve shown that cathodes don’t have to be layered,” Ceder said. “Suddenly we have a lot more chemical freedom, and I think that’s where the real excitement is because now we can do exploration of new cathodes.”

Superconductivity Gets A New Spin From University of Marlyand Physics Department

When you plug in an appliance or flip on a light switch, electricity seems to flow instantly through wires in the wall. But in fact, the electricity is carried by tiny particles called electrons that slowly drift through the wires. On their journey, electrons occasionally bump into the material’s atoms, giving up some energy with every collision.

The degree to which electrons travel unhindered determines how well a material can conduct electricity. Environmental changes can enhance conductivity, in some cases drastically. For example, when certain materials are cooled to frigid temperatures, electrons team up so they can flow uninhibited, without losing any energy at all – a phenomenon called superconductivity.

Now a team of researchers from the University of Maryland (UMD) Department of Physics, together with collaborators, has seen exotic superconductivity that relies on highly unusual electron interactions. While predicted to occur in other non-material systems, this type of behavior has remained elusive. The team’s research, published in the April 6 issue of Science Advances, reveals effects that are profoundly different from anything that has been seen before with superconductivity.

Electron interactions in superconductors are dictated by a quantum property called spin. In an ordinary superconductor, electrons, which carry a spin of 0.5, pair up and flow uninhibited with the help of vibrations in the atomic structure.

This theory is well-tested and can describe the behavior of most superconductors. In this new research, the team uncovers evidence for a new type of superconductivity in the material YPtBi, one that seems to arise from spin-3/2 particles.

“No one had really thought that this was possible in solid materials,” explains Johnpierre Paglione, a UMD physics professor and senior author on the study. “High-spin states in individual atoms are possible but once you put the atoms together in a solid, these states usually break apart and you end up with spin one-half. ”

Finding that YPtBi was a superconductor surprised the researchers in the first place. Most superconductors start out as reasonably good conductors, with a lot of mobile electrons – an ingredient that YPtBi is lacking. According to the conventional theory, YPtBi would need about a thousand times more mobile electrons in order to become superconducting at temperatures below 0.8 Kelvin. And yet, upon cooling the material to this temperature, the team saw superconductivity happen anyway. This was a first sign that something exotic was going on inside this material.

After discovering the anomalous superconducting transition, researchers made measurements that gave them insight into the underlying electron pairing. They studied a telling feature of superconductors – their interaction with magnetic fields.

As the material undergoes the transition to a superconductor, it will try to expel any added magnetic field from its interior. But the expulsion is not completely perfect. Near the surface, the magnetic field can still enter the material but then quickly decays away. How far it goes in depends on the nature of the electron pairing, and changes as the material is cooled down further and further.

To probe this effect, the researchers varied the temperature in a small sample of the material while exposing it to a magnetic field more than ten times weaker than the Earth’s. A copper coil surrounding the sample detected changes to the superconductor’s magnetic properties and allowed the team to sensitively measure tiny variations in how deep the magnetic field reached inside the superconductor.

The measurement revealed an unusual magnetic intrusion. As the material warmed from absolute zero, the field penetration depth for YPtBi increased linearly instead of exponentially as it would for a conventional superconductor.

This effect, combined with other measurements and theory calculations, constrained the possible ways that electrons could pair up. The researchers concluded that the best explanation for the superconductivity was electrons disguised as particles with a higher spin – a possibility that hadn’t even been considered before in the framework of conventional superconductivity.

The discovery of this high-spin superconductor has given a new direction for this research field. “We used to be confined to pairing with spin one-half particles,” says Hyunsoo Kim, lead author and a UMD assistant research scientist. “But if we start considering higher spin, then the landscape of this superconducting research expands and just gets more interesting.”

For now, many open questions remain, including how such pairing could occur in the first place. “When you have this high-spin pairing, what’s the glue that holds these pairs together?” says Paglione. “There are some ideas of what might be happening, but fundamental questions remain-which makes it even more fascinating.”